tiktoken is a BPE tokeniser for use with OpenAI's models. This is a pure JS port of the original tiktoken library.
Install the library from NPM:
npm install js-tiktoken
Basic usage follows, which includes all the OpenAI encoders and ranks:
import assert from "node:assert";
import { getEncoding, encodingForModel } from "js-tiktoken";
const enc = getEncoding("gpt2");
assert(enc.decode(enc.encode("hello world")) === "hello world");